Seagate ST340015A ユーザーズマニュアル

This command (EF

H

) controls the implementation of various features that the

drive supports. When the drive receives this command, it sets BSY, checks
the contents of the Features register, clears BSY and generates an interrupt.
If the value in the register does not represent a feature that the drive supports,
the command is aborted. Power-on default has the read look-ahead and write
caching features enabled. The acceptable values for the Features register are
defined as follows:

02

H

Enable write cache 

03

H

Set transfer mode (based on value in Sector Count register).

Sector Count register values:

00

H

Set PIO mode to default (PIO mode 2).

01

H

Set PIO mode to default and disable IORDY (PIO mode 2).

08

H

PIO mode 0

09

H

PIO mode 1

0A

H

PIO mode 2 

(default) 

0B

H

PIO mode 3

0C

H

PIO mode 4

20

H

Multiword DMA mode 0

21

H

Multiword DMA mode 1

22

H

Multiword DMA mode 2

40

H

Ultra DMA mode 0

41

H

Ultra DMA mode 1

42

H

Ultra DMA mode 2

43

H

Ultra DMA mode 3

44

H

Ultra DMA mode 4

45

H

Ultra DMA mode 5

55

H

Disable read look-ahead (read cache) feature.

82

H

Disable write cache.

AA

H

Enable read look-ahead (read cache) feature